The use of electromagnetic tomographic and spectrographic measurement devices have been identified in US Patent Publications 2013/0307564 and 2015/0137831 and U.S. Provisional Patent Application Nos. 61/703,488 and 61/932,400 (each of which is hereby incorporated by reference in its entirety) to locate specified volumes within a material under test (MUT), and to characterize that volume based upon its electromagnetic characteristics using two-terminal sensor arrays. A two-terminal sensor array consists of a positive and negative electrode pair conducting either a current or voltage signal through the MUT. The electrode configuration may consist of a single positive (transmitting) electrode and multiple negative (receiving) electrodes, where the single transmitting electrode and each of the receiving electrodes constitute a pair. In US Patent Publication 2012/0130212 (hereby incorporated by reference in its entirety), a four-terminal sensor array is presented to measure blood metabolite levels. Where the location of the spectroscopy measurement can be selected such that the signal has desired or target impedance properties, the data and resulting conclusions may be useful. For example, where the desire is to measure blood metabolites, the area selected for measurement should have the greatest volume of blood in the measurement area.